Absolute acceleration sensor for use within moving vehicles

ABSTRACT

A communication system for a vehicle includes a vehicle speed sensor configured to emit a periodic function with a parameter correlated to the speed of the vehicle, an acceleration monitoring system, a braking system engagement detector to detect a braking status of the vehicle, an alerting device capable of signaling other drivers of a deceleration condition of the vehicle, and a control device. The acceleration monitoring system is configured to compute the acceleration of the vehicle from variations in the parameter of the periodic function of the vehicle speed sensor and to output a deceleration status of the vehicle. The control device is coupled to the acceleration monitoring system, the braking system engagement detector, and the alerting device, wherein the acceleration monitoring system sends signals to the control device and the control device operates the alerting device in a manner dependent on the deceleration status of the vehicle.

RELATED APPLICATION

This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 11/243,364, filed Oct. 3, 2005 and entitled,“ABSOLUTE ACCELERATION SENSOR FOR USE WITHIN MOVING VEHICLES”, which ishereby incorporated by reference in its entirety, and which claimspriority under 35 U.S.C. 119(e) of the co-pending U.S. provisionalpatent application, Application No. 60/616,400, filed on Oct. 5, 2004,and entitled “REAR-END COLLISION AVOIDANCE SYSTEM,” which is also herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to methods and devices fordetecting absolute levels of longitudinal, lateral and verticalacceleration within moving vehicles, and to a variety of systems andmethods for generating responses to changes in these absolute levels.

BACKGROUND OF THE INVENTION

Accelerometers find a wide variety of applications within modern motorvehicles. The most common of these are impact and collision sensors usedto deploy front and side impact air bags in modern passenger cars andtrucks.

In applications that depend on sudden and drastic deceleration, thepresence of gravity is of little consequence and will not affect theimplementation of the accelerometer. However, increasingly feedbacksystems within motor vehicles have attempted to make use ofaccelerometer data during much lower and subtler levels of acceleration.

One example is anti-collision warning systems. Though all street legalmotor vehicles have brake lamps configured to signal other drivers ofbraking, these signals do not warn following drivers of imminentbraking. At least one system has proposed activating a vehicle's brakelamp system in response to a deceleration signal from a sensitiveaccelerometer, and independent of actuation of the brake pedal. Thesystem described in U.S. Pat. No. 6,411,204 to Bloomfield et al.,entitled “DECELERATION BASED ANTI-COLLISION SAFETY LIGHT CONTROL FORVEHICLE,” includes a plurality of deceleration thresholds each with anassociated modulation of the brake lamps.

However, the system fails to precisely account for gravitational forces,limiting its effectiveness to deceleration regimes where gravity'seffect is minimal and reducing its effectiveness as an early warningsystem. Accelerometers, known as tilt sensors in the gaming and roboticsindustries, are extremely sensitive to any gravitational force to whichthey are not perpendicular. This sensitivity complicates any system thatattempts to detect low levels of acceleration by using accelerometerswithin moving vehicles, since the system must account for the widevariety of orientations of the accelerometer relative to the earth'sgravity introduced as the vehicle travels uphill, downhill, throughcambered or off-camber curves, and on cambered grades. For instance, anaccelerometer in a vehicle stopped on a 45-degree downhill slope wouldsense deceleration of a magnitude equal to 0.71 times the accelerationdue to gravity. To avoid gravitational acceleration artifacts, thesystem of Bloomfield only produces output if the deceleration signalrises above a predetermined threshold set above the level of artifactsintroduced during typical driving conditions.

However, the reliance of this device on a threshold deceleration reducesits effectiveness as an early warning system. Even a short delay betweenthe time when the subject vehicle begins to slow down and the time whena following vehicle begins to slow can result in a rapid closure of thegap, or following distance, between the vehicles, and a potentialcollision. Consequently, the shorter the following distance betweenvehicles, the smaller the margin of error will be for drivers offollowing vehicles to avoid rear-end collisions. Disengaging theaccelerator, or coasting, is often the first response of the driver of asubject vehicle to observing a non-urgent traffic event in the roadwayahead, and usually results in a slight deceleration. By failing to warnother drivers of the possible imminence of braking of a subject vehicle,the proposed device loses valuable time. To avoid this problem, thethreshold must be set lower, which could result in gravitationalacceleration artifacts affecting the system's output. For example, anoverly low threshold could prevent the device from signalingdeceleration on an uphill grade since the accelerometer would sense acomponent of the earth's gravity as acceleration. Similarly, a lowthreshold could cause the device to continuously flash during a descent,while gravity appears as deceleration.

The loss of time incurred by a threshold-based system might be tolerablein some other application; but in collision prevention, even an instantsaved can prevent a collision. A Special Investigative Report issued inJanuary of 2001 by the National Transportation Safety Board (NTSB)illustrates the scale of the problem. The report notes that in1999“1.848 Million rear-end collisions on US roads kill[ed] thousandsand injur[ed] approximately [one] Million people.” The report concludedthat even a slightly earlier warning could prevent many rear-endcollisions.

-   -   Regardless of the individual circumstances, the drivers in these        accidents were unable to detect slowed or stopped traffic and to        stop their vehicles in time to prevent a rear-end collision. If        passenger car drivers have a 0.5-second additional warning time,        about 60 percent of rear-end collisions can be prevented. An        extra second of warning time can prevent about 90 percent of        rear-end collisions. [NTSB Special Investigative Report        SIR-01/01, Vehicle-and Infrastructure-based Technology for the        Prevention of Rear-end Collisions]

SUMMARY OF THE INVENTION

In this application “acceleration” refers to either or both positiveacceleration and negative acceleration (sometimes called“deceleration”), while “deceleration” refers to only negativeacceleration.

The present invention provides systems and methods for warning driversof other vehicles of any possibility that a subject vehicle will brakeand/or that the following vehicle may need to decelerate. This warningoccurs earlier than warnings provided by traditional rear brake warningsystems. The preferred embodiment of the present invention takesadvantage of the existing conditioning of modern drivers to respondquickly to rear brake warning lamps by using these systems to convey newdeceleration warnings.

Some embodiments of the present invention relate to devices thatovercome the limitations of the prior art by integrating the signalsfrom pulse or sine wave generators, which are directly related tovehicle distance traveled. These devices are commonly referred to asvehicle speed sensors (VSS). Most modern vehicles are shipped with anelectronic VSS as standard equipment. The stock VSS communicates withthe vehicle's electronic control module (ECM) and speedometer to displaythe speed of the vehicle to an operator. However, a VSS can be installedas an aftermarket add-on.

The embodiments of the present invention involve using signals from avehicle's VSS to detect deceleration of the vehicle, and modulatingwarning lights of the vehicle in response to the vehicle's decelerationPreferably, the VSS emits a periodic function with a parametercorresponding to the vehicle's speed. For example, some embodiments ofthe present invention use a VSS that outputs a DC pulse with a frequencythat corresponds to the speed of the vehicle. In addition, someembodiments of the present invention use a VSS that outputs an AC sinefunction with a frequency that corresponds to the speed of the vehicle.

In one aspect, the present invention relates to a vehicle communicationsystem. The vehicle communication comprises the following: a vehiclespeed sensor configured to emit a periodic function with a parametercorrelated to the speed of the vehicle; an acceleration monitoringsystem, configured to compute the acceleration of the vehicle from theperiodic function of the vehicle speed sensor and to output adeceleration status of the vehicle; a braking system engagement detectorto detect a braking status of the vehicle; an alerting device capable ofsignaling other drivers of a deceleration condition of the vehicle; anda control device coupled to the acceleration monitoring system, thebraking system engagement detector, and the alerting device, wherein theacceleration monitoring system sends signals to the control device andthe control device operates the alerting device in a manner dependent onthe deceleration status of the vehicle. Preferably, the parameter is afrequency of the periodic function. In some embodiments the parameter isa pulse width of the periodic function.

Some embodiments of the present invention relate to a method of alertingdrivers in proximity to a vehicle of deceleration and braking of thevehicle. The method includes steps of sensing a speed of the vehicle;producing a periodic function with a parameter correlated to the speedof the vehicle; determining a rate of acceleration of the vehicle basedon variations in the parameter of the periodic function; detecting abraking status of the vehicle; detecting a throttle status of thevehicle; and if the vehicle is decelerating, emitting a signal toindicate that the vehicle is decelerating, wherein the signal variesdepending on the rate of deceleration, the braking status, and thethrottle status of the vehicle.

The periodic function emitted by a VSS preferably has a pulse widthassociated with its frequency. Some embodiments of the present inventionmeasure changes in pulse width to determine deceleration. Someembodiments measure changes in frequency to determine deceleration. Someembodiments incorporate both pulse width and frequency in determiningdeceleration.

In the embodiments that measure changes in pulse width to determinedeceleration, the distance or width between a first pulse and a secondpulse is compared to the distance or width between the second pulse anda third pulse. If the width is longer in duration than the previouswidth then the vehicle is decelerating. If the width is shorter then theprevious width then the vehicle is acceleration. If the pulses are equalin width then the speed of the vehicle is constant.

The present invention also provides systems that adjust suspension of avehicle while turning in response to data from an accelerometer. In someembodiments, a gyroscope is used to detect whether the vehicle isturning or not.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a single axis accelerometer positioned for measuringlateral acceleration, and included in an accelerometer-gyroscopic sensorin accordance with an embodiment of the present invention.

FIG. 1B illustrates a dual axis accelerometer positioned for measuringvertical and longitudinal acceleration, and included in anaccelerometer-gyroscopic sensor in accordance with an embodiment of thepresent invention.

FIG. 2A illustrates a gyroscope positioned for measuring a heading, andincluded in an accelerometer-gyroscopic sensor in accordance with anembodiment of the present invention.

FIG. 2B illustrates a gyroscope positioned for measuring a lateralinclination, and included in an accelerometer-gyroscopic sensor inaccordance with an embodiment of the present invention.

FIG. 2C illustrates a longitudinal inclination, and included in anaccelerometer-gyroscopic sensor in accordance with an embodiment of thepresent invention.

FIG. 3A is a schematic view illustrating the components of the rear-endcollision avoidance system, warning drivers of a subject vehicle'sdeceleration, in accordance with an embodiment of the present invention.

FIG. 3B illustrates a state machine diagram of the control device inaccordance with the preferred embodiment of the present invention.

FIG. 3C illustrates a state machine diagram of the control device inaccordance with an alternative embodiment of the present invention.

FIG. 4 illustrates a schematic view of an anti-rollover system inaccordance with an embodiment of the present invention.

FIG. 5 illustrates a schematic view of an engine performance monitoringsystem in accordance with an embodiment of the present invention.

FIG. 6 illustrates a schematic view of a suspension and road conditionmonitoring system in accordance with an embodiment of the presentinvention.

FIG. 7 illustrates a navigation system in accordance with an embodimentof the present invention.

FIG. 8 illustrates a schematic view of an anti-rollover system inaccordance with an embodiment of the present invention.

FIG. 9 is a schematic view illustrating the components of the rear-endcollision avoidance system, warning drivers of a subject vehicle'sdeceleration, in accordance with the preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1B and 2C, one embodiment of the present inventionincludes a dual axis accelerometer and an electronic gyroscopepositioned upon a moving body (not shown) having a pitch axis and a yawaxis that form a pitch-yaw plane as illustrated, which attempts to movealong a movement vector orthogonal to the pitch-yaw plane. A first axis,termed the longitudinal axis, of the dual axis accelerometer is placedorthogonal to the plane of the pitch and yaw axes to sense accelerationalong the movement vector. A second axis, termed the vertical axis, ofthe accelerometer is placed parallel with the yaw axis (and thusperpendicular to the movement vector) to sense acceleration along theyaw axis. Thus the two axes of the accelerometer form alongitudinal-vertical plane orthogonal to the pitch-yaw plane.

The gyroscope in FIG. 2C is mounted parallel to thelongitudinal-vertical plane of the accelerometer and thus is also alonga plane perpendicular to the pitch-yaw plane of the moving body. Thisconfiguration allows it to sense an inclination of the movement vectorof the moving body relative to the gravitational acceleration acting onthe body.

In some embodiments of the present invention, an accelerometer is usedto detect additional types of movement. The orientation shown in FIG. 1Aallows for detection of lateral acceleration. In FIG. 1A, a single axisaccelerometer configured with a first axis, termed the lateral axis,parallel to the pitch axis senses lateral acceleration of the body, e.g.acceleration in a plane orthogonal to the longitudinal-vertical plane.

When the body does undergo a lateral acceleration, its actual movementis no longer along the desired movement vector. Thus, during lateralacceleration, another gyroscope can be included to sense the inclinationof the component of the actual movement vector that lies along thelateral axis. FIG. 2B depicts a gyroscope configured parallel to thepitch-yaw plane and thus configured to detect an inclination of thecomponent of movement that lies along the lateral axis, termed thelateral inclination of the body.

In some embodiments, the system also includes another gyroscope that isconfigured parallel to the lateral-longitudinal plane (in which alldesirable movement vectors will lie), to detect a heading of the body.This additional gyroscope is required for those embodiments that supplysupplemental data to navigation systems.

Preferably, the embodiments of the present invention include logiccircuits configured to receive signals of acceleration along thelateral, longitudinal, and vertical axes, as well as of the lateral andlongitudinal inclinations and the heading, if necessary and to processthese signals to produce a variety of output signals indicatingcharacteristics of the moving body's movement. These preferably include:absolute longitudinal acceleration (both positive and negative),absolute vertical acceleration (both positive and negative), absolutelateral acceleration (both positive and negative), heading, and actualspeed.

Though accelerometers are inherently stable, and especially so wheninternally temperature compensated, gyroscopes, both mechanical andelectronic, can suffer from instability and drift. Because of thesedrift characteristics, gyroscopes typically require periodicauto-zeroing or re-referencing to provide reliable output.

In some embodiments of the present invention, a method of detecting anabsolute deceleration includes steps of re-referencing. This task ispreferably accomplished using signals from the accelerometers, but inother embodiments use a Hall effect, electronic or other type ofcompass.

Re-referencing preferably takes place periodically; for systems usingHall effect or some other independent compass, the systems simplyre-reference at specified heading or timing intervals. However, systemsthat use accelerometer data for re-referencing are preferably morecareful. When stationary, any signal from the accelerometer isessentially representative of the earth's gravity, this signal canprovide an initial reference for any gyroscopes included in the presentinvention, which preferably takes place prior to movement of the body.

Once the body has begun moving, without periodic re-referencing, thegyroscope output can become unreliable. The present invention teachesseveral methods of re-referencing during travel. Some of these are onlyapplicable to travel that includes periodic stops. For example, thevertical or lateral axis accelerometers can be used to detect whetherthe body is stopped. When it is stopped, the signal from thelongitudinal axis of the accelerometer can be used to re-reference thegyroscope. Further, at any point during travel when no acceleration hasbeen detected for a predetermined period of time the gyroscope can bere-referenced. In this way repeated referencing can occur even duringextended travel without any stops.

The present invention is preferably implemented in a vehicle, and thefollowing embodiments of the present invention are described relative toa vehicle. However, the methods and systems taught by the presentinvention can be implemented in a wide variety of moving bodies otherthan vehicles.

Example 1 Rear End Collision Avoidance

FIG. 3A is a schematic view illustrating the components of the rear-endcollision avoidance system 300, warning drivers of a subject vehicle'sdeceleration, in accordance with one embodiment of the presentinvention. The rear-end collision avoidance system 300 comprises anaccelerometer-gyroscopic sensor 310, a braking system engagementdetector 320, a throttle engagement detector 330, and a control device340. The accelerometer-gyroscopic sensor 310 is coupled to the controldevice 340, detects an absolute longitudinal deceleration of thevehicle, and sends a signal to the control device 340. The brakingsystem engagement detector 320 is also coupled to the control device340, detects any engagement of the braking system of the vehicle, andsends a signal to the control device 340. The throttle engagementdetector 330 is also coupled to the control device 340 and detectsengagement of the throttle. In alternative embodiments, the presentinvention also includes additional input devices, such as a clutchengagement detector configured to relay a clutch status to the controldevice 340. Next, the control device 340 processes the input signals itreceives from the accelerometer-gyroscopic sensor 310, the brakingsystem engagement detector 320, and the throttle engagement detector 330and decides whether to activate an alerting device of the vehicle. Insome embodiments the control device 340 only activates an alertingdevice if the vehicle is throttled down but not braking. In someembodiments, the control device 340 activates the alerting device onlyif the absolute longitudinal deceleration is non-zero. In oneembodiment, the communication system further comprises an alertingdevice activation circuit 350, wherein the control device 340 is coupledto and sends signals to the alerting device activation circuit 350,which activates an alerting device based on a signal from the controldevice 340.

In some other embodiments, input from a vehicle speed sensor (VSS) isused to perform a similar function. FIG. 9 is a schematic viewillustrating the components of the rear-end collision avoidance system900, warning drivers of a subject vehicle's deceleration, in accordancewith one embodiment of the present invention. The rear-end collisionavoidance system 900 comprises a vehicle speed sensor 910, anacceleration monitoring system 915, a braking system engagement detector920, and a control device 940. In some embodiments, the rear-endcollision avoidance system 900 also includes a throttle engagementdetector 930.

The vehicle speed sensor 910 is coupled to the acceleration monitoringsystem 915, which is coupled to the control device 940. The vehiclespeed sensor 910 detects a speed of the vehicle and emits a periodicfunction with a frequency that is correlated to the speed of thevehicle. The acceleration monitoring system 915 uses variations in theperiodic function to calculate the acceleration (or deceleration) of thevehicle. The acceleration monitoring system 915 sends a signal to thecontrol device 940 that represents deceleration of the vehicle. Thebraking system engagement detector 920 is also coupled to the controldevice 940, detects any engagement of the braking system of the vehicle,and sends a signal to the control device 940. If present, the throttleengagement detector 930 is also coupled to the control device 940 anddetects engagement of the throttle. In alternative embodiments, thepresent invention also includes additional input devices, such as aclutch engagement detector configured to relay a clutch status to thecontrol device 940. Next, the control device 940 processes the inputsignals it receives from the acceleration monitoring system 915, thebraking system engagement detector 920, and the throttle engagementdetector 930 and decides whether to activate an alerting device of thevehicle. In some embodiments the control device 940 only activates analerting device if the vehicle is throttled down but not braking. Insome embodiments, the control device 940 activates the alerting deviceonly if the absolute longitudinal deceleration is non-zero. In oneembodiment, the communication system further comprises an alertingdevice activation circuit 950, wherein the control device 940 is coupledto and sends signals to the alerting device activation circuit 950,which activates an alerting device based on a signal from the controldevice 940.

The preferred embodiment uses a microprocessor or micro-controller asthe acceleration monitoring system 915 to measure pulse widthdifferentials between consecutive pulses. If the periodic functionproduced by the VSS is a DC pulse, only one wire is needed to interfacewith the VSS 910. If the periodic function is an AC sine wave two wiresare used.

The functions of the preferred embodiment illustrated with reference toFIG. 9 are preferably performed in a module that contains variousdiscrete electronic components involved in signal conditioning as wellas a microprocessor or microcontroller, which would actually do thecomputations. Preferably, these include one or more of the following: amicroprocessor, interpreter, voltage regulator, RAM, EEPROM, resonatorand communication port and circuitry along with various filtering andvoltage protection circuitry. Preferably, the module is capable ofaccurately measuring and comparing pulse widths of 1 millionth of asecond or less and frequencies of zero (0) to megahertz all within timeframes of micro to milliseconds. Though the present invention can beimplemented in an analog or electromechanical circuit, the preferredembodiment is implemented in a digital circuit including programmableelements.

In addition, in some embodiments the various embodiments described aboveare implemented in a module that includes a separate aftermarket VSS.These embodiments are advantageous when used to retrofit older vehiclesthat do not come with a VSS as original equipment.

In addition, some embodiments use an aftermarket VSS, even on newervehicles. For example, one such VSS comprises a sensor configured todetect rotation of the universal joint of a motor vehicle. Someembodiments use similar sensors to detect rotation of other movingparts.

In this embodiment, a sensor is mounted on either the rear-end housingor on the back end of the transmission and where the sensor ispositioned over the universal joint. The sensor would not be in contactwith the spinning universal joint but in close proximity, e.g. ⅛ or ¼inch air gap.

The sensor is preferably configured to sense ferrous metal. Thus, thereis no need to affix anything to the actual spinning universal joint.Universal joints typically have four protrusions. The sensor isoptionally configured to sense either two or four of the protrusions.The resultant signal represents variations in the magnetic flux fieldproduced by the sensor each time a protrusion passes through themagnetic field.

One type of sensor used in some embodiments of the present inventioncomprises a coil with or without a core. When a voltage is applied tothe coil, a magnetic flux field is produced around the coil. If aferrous metal object passes through that field it robs just a little ofthe power (which is stored in the field) resulting in a change in thecurrent and voltage within the coil and conductor feeding the coil. Thissignal is then used to produce a square wave.

The embodiments of the present invention include input devices. Thosementioned above include braking system engagement detectors, throttleengagement detectors, the accelerometer-gyroscopic sensor, andVSS/acceleration monitoring systems. In alternative embodiments, thepresent invention also includes additional input devices, such as aclutch engagement detector configured to relay a clutch status to thecontrol device.

The embodiments of the present invention include alerting devices. Inthe present invention, an alerting device preferably comprises lamps onthe vehicle that are capable of flashing and emitting visible light. Inone aspect, the lamps of the alerting device flash only at a constantrate, while in another aspect the lamps flash at a variable rate, andfurther wherein the control device is configured to flash the lamps at arate correlated to a rate of deceleration. The lamps are preferably oneof the following: conventional signaling lamps and conventional brakelamps. However, in another embodiment, the alerting device is a radiofrequency (RF) transmitter capable of directing RF signals from the rearof the vehicle to a following vehicle. In other embodiments, thealerting device uses other types of non-visible radiation for signaling.Preferably, the proximate vehicles include a device for receiving thenon-visible radiation and generating an alert signal to notify thedriver of the deceleration.

For example, in some other embodiments, the signaling lamps usedcomprise bi-color light emitting diodes (LED). In these embodiments, thebi-color LEDs change color depending on the polarity of the current usedto energize them. Thus, the control device in these embodiments isconfigured to provide current to the bi-color LEDs with a polarity thatvaries depending on the signal to be sent. For example, in oneembodiment the control device leaves the bi-color LEDs un-energized whenno deceleration is occurring and the brakes are not engaged, provides acurrent with a polarity to cause the bi-color LEDs to emit a yellowlight upon deceleration, and to provide a current with a polarity tocause the bi-color LEDs to emit a red light upon braking.

When used in this patent, the terms “conventional signaling lamps” and“conventional brake lamps” refer to signaling or brake lamps of the typeincluded on motor vehicles during their original manufacture. Thepresent invention also contemplates signaling by using after-marketdevices that are attached to a vehicle in addition to conventionalsignaling and brake lamps.

A communication system can be embodied as an after-market add-on productor as an original vehicle system. These embodiments include differenttypes of controllers. In an add-on system, a control device preferablydoes not interfere with the existing brake lamp system controller. Thecontrol device communicates with the brake lamps in a substantiallyseparate manner from the existing brake lamp control system. Controldevices used in the present invention could include relays, switches ormicro controllers. In one aspect, an aftermarket system can continuouslypower the alerting device activation circuit without need of anintermediate control device.

However, in an original equipment system, a communication system inaccordance with the present invention preferably includes a controldevice that further comprises a control system for the conventionalbrake lamp system, whereby the communication system is an integratedcontrol and circuitry system for all brake lamps. In this aspect, asingle control system accomplishes the tasks of conventional brakesignaling and the signaling described in the present invention.

During operation, the communications system of the present inventionuses information from the various input devices to determine a manner inwhich to operate an alerting device. In one aspect, the communicationssystem continuously modulates the alerting device based on theaccelerometer-gyroscopic sensor's input so long as the throttle isdisengaged, regardless of braking system status. In another aspect, oncethe braking system is engaged, the communications system activates thealerting device continuously until disengagement of the braking system,whereupon the communications system once again considers throttle andthe accelerometer-gyroscopic sensor's input in choosing a manner inwhich to operate the alerting device. In a third aspect, where aconventional braking system exists separately from a communicationssystem as described in the present invention, the control devicedeactivates in response to braking system engagement and reactivatesupon braking system disengagement. Preferably, the control devicereceives input in cycles and makes a determination for operation of thealerting device within each cycle.

In one embodiment, the control device 940 takes input from theacceleration monitoring system 915, the braking system engagementdetector 920, and the throttle engagement detector 930 in cycles thatare substantially continuous in time. In the preferred embodiment, foreach cycle, the control device 940 enters one of four states: I) it doesnot activate an alerting device for the entirety of the cycle, II) itactivates an alerting device for the entirety of the cycle, III) itactivates an alerting device at least once for a period of time that isshort relative to the duration of the cycle; or IV) it activates analerting device multiple times during the cycle.

FIG. 3B illustrates a preferred embodiment in which these four outputstates are handled. A state machine 301, included in a control device inaccordance with the present invention, takes five possible input states,for four of them throttle status is not considered: 1) brake pedal isnot depressed, deceleration is not detected; 2) brake pedal is notdepressed, deceleration is detected; 3) brake pedal is depressed,deceleration is detected; or 4) brake pedal is depressed, decelerationis not detected. State 5) only occurs if the throttle is disengaged, andif the brake pedal is not depressed. Input state 1 corresponds to outputstate I, input state 2 corresponds to output state III, input states 3and 5 correspond to output state II, and input state 4 corresponds tooutput state IV.

Transitions between all input states are handled and every transition isa plausible outcome of a braking or acceleration event. For example, adriver disengaging the throttle pedal causes a transition from state 1to state 5. In the first cycle detecting state 5, the brake lamps areilluminated. Once a required level of deceleration is detected, atransition from state 5 to state 2 occurs. In the first cycle detectingstate 2, the brake lamps are flashed, or another alerting device isactivated, corresponding to output state III. A transition from state 1directly to state 2 can occur when beginning ascent of a steep grade:the throttle is engaged, the brake pedal is disengaged but the vehiclebegins to decelerate.

If the driver engages the throttle again, or in the case of an ascent,increases the throttle, a transition from state 5 to state 1, or state 2to state 1, occurs. If the driver subsequently depresses the brakepedal, a transition from state 2, or state 5, to state 3 occurs. Whilethe brake pedal is depressed, state II output keeps the brake lampsilluminated. Furthermore, while the brake pedal is depressed, atransition from state 3 to state 4 may occur. In this embodiment, instate 4 the lamps are flashed at an increased rate. Whenever the brakepedal is depressed, state II or IV output occurs andaccelerometer-gyroscopic sensor data is effectively ignored. When thebrake pedal is released, one of input state 1, input state 2, and inputstate 5 are entered.

A transition from input state 3 to 2 corresponds to tapping or pumpingthe brake pedal. Depending on the length of time a cycle comprises, aresidual brake lamp flash may occur. Transitions from input states 3 or4 to state 1 correspond respectively to accelerating from a rolling stopon a hill, or rolling forward downhill. A transition from input state 4to 2 could arise when rolling down a hill backwards, for example at astoplight on a hill. This points to another feature of the currentsystem—providing a warning for rollback.

In the alternative embodiment illustrated in FIG. 3C, a state machine301′ included in a control device in accordance with the presentinvention, the system only considers the first three states. The statemachine 301′ takes four possible input states: 1) brake pedal is notdepressed, deceleration is not detected; 2) brake pedal is notdepressed, deceleration is detected; 3) brake pedal is depressed,deceleration is detected; or 4) brake pedal is depressed, decelerationis not detected. Input state 1 corresponds to output state I, inputstate 2 corresponds to output state III, and input states 3 and 4correspond to output state II.

Transitions between all input states are handled and every transition isa plausible outcome of a braking or acceleration event. For example, adriver taking his or her foot off the accelerator pedal causes atransition from state 1 to state 2. In the first cycle detecting state2, the brake lamps are flashed, or other alerting means are activated,corresponding to output state III. This transition from state 1 to state2 also occurs when beginning ascent of a steep grade: the accelerator isdepressed, the brake pedal is disengaged but the vehicle begins todecelerate. If the driver presses the accelerator again, or in the caseof an ascent, further depresses the accelerator, a transition from state2 to state 1 occurs. If the driver subsequently depresses the brakepedal, a transition from state 2 to state 3 occurs. While the brakepedal is depressed, state II output keeps the brake lamps illuminated.Furthermore, while the brake pedal is depressed, a transition from state3 to state 4 may occur. In this embodiment, such a transition results inno change in output. Whenever the brake pedal is depressed, state IIoutput occurs and accelerometer-gyroscopic sensor data is effectivelyignored. When the brake pedal is released, either input state 1 or inputstate 2 is entered.

Transitions between states in this embodiment are similar to those inthe preferred embodiment. A transition from input state 3 to 2corresponds to tapping or pumping the brake pedal. Depending on thelength of time a cycle comprises, a residual brake lamp flash may occur.Transitions from input states 3 or 4 to state 1 correspond respectivelyto accelerating from a rolling stop on a hill, or rolling forwarddownhill. A transition from input state 4 to 2 could arise when rollingdown a hill backwards, for example at a stoplight on a hill. This pointsto another feature of the current system—providing a warning forrollback.

Embodiments of the present invention provide the driver of a subjectvehicle a communication system that provides warning signals to othervehicles of any deceleration or possibility of braking of the subjectvehicle. One novel and distinguishing feature of this invention is thatthe subject vehicle's communication system warns other vehicles of anypossibility that the subject vehicle will begin to brake. This is sobecause any engagement of the brake pedal is usually immediatelypreceded by a disengagement of the throttle.

Thus, this invention provides an earlier warning to the driver of thefollowing vehicle of a subject vehicle's intent to decelerate than iscurrently available in modern vehicles, which only provide systems thatactuate warning lamps if the driver depresses the brake pedal or if anaccelerometer unit detects a threshold deceleration. Modern driversrespond quickly to rear brake warning lamps, conditioning that thepresent invention takes advantage of by using these warning systems toconvey new and broader warnings. Since following distances on modernroadways are often inadequate, this arrangement could prevent numerousrear-end collisions.

Example 2 Anti-Rollover Systems

In some embodiments of this invention, outputs from the sensing ofabsolute lateral acceleration are used to adjust suspension systems bystiffening outside suspension and/or loosening inside suspension ofmoving vehicles. Further, in some other embodiments, simple lateralacceleration is used to adjust suspension systems during turning.

When lateral acceleration or force is applied to a vehicle, it tends tolean in the direction opposite to the force being applied, due in partto the softness of their suspension systems. This moves the center ofgravity further off center and in some cases outside of their wheelbaseapproaching the critical rollover point. Stiffening the outsidesuspension and/or loosening the inside suspension keeps the center ofgravity of vehicles within a tighter envelope relative to the wheelbase.This inversely affects the propensity, especially in high center ofgravity loaded vehicles, to rollover when the center of gravity of theirload exceeds the wheelbase and reaches the critical rollover point.Additionally, by adjusting the suspension system in this manner thedistribution of load between left and right side wheels is kept moreeven resulting in improved traction.

The above can be accomplished either with an absolute lateralacceleration signal and a gyroscopic correction, or with an uncorrectedlateral acceleration signal. In the latter scenario, an accelerometermounted to sense lateral acceleration also detects a component ofgravitational acceleration during a banked turn. The strength of thegravitational component relative to the lateral (centrifugal)acceleration will depend on the speed of the turn. Correction to thesuspension system is performed accordingly. In addition, this type ofsuspension adjustment system could be used only when the vehicle isturning. A gyroscope mounted in the horizontal plane to sense heading(e.g. FIG. 2A) could be used to sense whether the vehicle is turning ornot. In

Typically these are configured as pulse width modulated (PWM)controlling devices. Such devices typically accept analog voltage levelinputs, which are then converted to a corresponding pulse width output.Such outputs are a common method of controlling and delivering aregulated amount of current to a device such as a hydraulic solenoid.The hydraulic solenoids of course are responsible for increasing,decreasing or maintaining pressure levels within the hydraulic orpneumatic suspension system.

An anti-rollover device 400 using an absolute acceleration signal isillustrated in FIG. 4. In this embodiment vehicles are assumed to beequipped with adjustable suspension systems, typically hydraulic orpneumatic. When absolute lateral acceleration is sensed theaccelerometer-gyroscopic sensor 410 sends a signal representing absolutelateral acceleration to a suspension selector 420, which passes signalsalong to a controller responsible for controlling the relevant quadrantof the suspension. The suspension selector 420 must interpret the signalto determine the appropriate quadrant. For example, Q1, in whichsuspension system 432 is controlled by suspension control 431 could bethe right front wheel; Q2, in which suspension system 442 is controlledby suspension control 441 could be the left front wheel; Q3, in whichsuspension system 452 is controlled by suspension control 451 could bethe right rear wheel; and Q4, in which suspension system 462 iscontrolled by suspension control 461 could be the left rear wheel. Ofcourse, other orderings are possible, as are systems with only twoindependent zones, e.g. two sides are controlled in lockstep.

An anti-rollover device 800 using a lateral accelerometer is illustratedin FIG. 8. In this embodiment vehicles are assumed to be equipped withadjustable suspension systems, typically hydraulic or pneumatic. Whenlateral acceleration is sensed the accelerometer 810 sends a signalrepresenting lateral acceleration to a suspension selector 820, whichpasses signals along to a controller responsible for controlling therelevant quadrant of the suspension. The suspension selector 820 mustinterpret the signal to determine the appropriate quadrant. For example,Q1, in which suspension system 832 is controlled by suspension control831 could be the right front wheel; Q2, in which suspension system 842is controlled by suspension control 841 could be the left front wheel;Q3, in which suspension system 852 is controlled by suspension control851 could be the right rear wheel; and Q4, in which suspension system862 is controlled by suspension control 861 could be the left rearwheel. Of course, other orderings are possible, as are systems with onlytwo independent zones, e.g. two sides are controlled in lockstep.

Example 3 Performance Monitoring Systems

Due to fuel efficiency goals and competitive pressures late modelvehicles have the ability to monitor engine system performance throughan array of sensors and detectors. The absolute accelerometer/gyroscopecombination provides the ability to communicate actualpower-to-the-ground data for use in engine/vehicle performancecomputations. In this embodiment, the accelerometer-gyroscopic sensorcontinuously sums absolute acceleration values to provide both absoluteacceleration and actual speed values, which can be used by amanufacturers vehicle computer unit (VCU).

For example, the system 500 shown in FIG. 5 includes theaccelerometer-gyroscopic sensor 510, which delivers actual speed dataand absolute acceleration data to a vehicle computer unit (VCU) 520 (orat least the engine monitoring portion thereof). The VCU 520 usesbaseline engine performance data 540 to either self-correct through afeedback mechanism, or to issue a warning through the performancewarning system.

The manufacturer's baseline engine performance data is helpful indetermining how much acceleration should be achieved for a given amountof throttle and what the speed of the vehicle should be for a givenamount of throttle. For instance, a VCU may have tuned to maximumefficiency however the vehicle's corresponding speed or acceleration maybe many percentage points less than what would be expected, indicatingperhaps that the tire pressure is low or that the vehicle is loaded to ahigher level than what would be normal, in which case the tire pressureshould be increased.

Example 4 Road or Suspension Condition Monitoring Systems

Because an accelerometer-gyroscopic sensor, which is used and is part ofthis invention can use one axis of a dual axis accelerometer in thevertical position vertical acceleration output signals are madeavailable to other monitors or computers that require this information.Such a requirement may be to monitor and evaluate road quality and/orshock absorber utilization and performance. For instance, it is apparentto a rider in a vehicle when such vehicle is riding on worn out shockabsorbers. However, it becomes less apparent when those shock absorberswear out slowly over an extended period of time. The first time a drivermay realize that shock absorbers have worn out is in cases wherecritical performance is required. Or when they replace worn out tiresand see the evidence on tires of worn out shock absorbers. The absoluteA/G sensor detects vertical acceleration in very small increments.Increasing levels of vertical acceleration can easily be monitored thusproviding notice to drivers of the degradation of shock absorber system.

For example, in the system 600 shown in FIG. 6, theaccelerometer-gyroscopic sensor 610 provides absolute verticalacceleration data to a VCU 620 or at least a suspension-monitoringportion thereof. The VCU 620 can use baseline suspension performancedata 640 to either self-correct through a feedback mechanism or issue awarning through the suspension warning system 630.

Example 5 Navigation Systems

In most embodiments, the accelerometer-gyroscopic sensor is continuouslymonitoring acceleration; a unit of acceleration multiplied by a unit oftime yields a unit of velocity (with speed as its magnitude).Preferably, the accelerometer-gyroscopic sensor continuously sums unitsof acceleration over small increments of time. In this case, theaccelerometer-gyroscopic sensor provides the integrated velocity orspeed as an output. Preferably, when a horizontally mounted gyroscope isincorporated, the accelerometer-gyroscopic sensor also providesdirection or heading as an output.

Because velocity, or speed and heading are the raw elements required forinertial navigation systems. In the system 700 shown in FIG. 7, theaccelerometer-gyroscopic sensor 710 provides actual speed and headinginformation as an output to a navigation system controller 720. Thenavigation system controller 720, which normally provides navigationdata from a global positioning system (GPS) 730 directly to thenavigation system input/output (I/O) 750, incorporates headinginformation from the accelerometer-gyroscopic sensor 710 during periodsof connection loss with the GPS satellite system. In return forproviding the heading data to the inertial navigation system 740, thenavigation controller receives navigation data from the inertial systemto supplement or replace its GPS data.

Preferably, the navigation system controller 720 also provides GPSheading data back to the accelerometer-gyroscopic sensor 710 to permitre-referencing of the gyroscopes contained therein. Continuousreferencing and re-referencing of the horizontally mounted gyroscopeutilize GPS heading values while satellite signals are acquired. Oncesatellite signals are lost gyroscopic heading values take priority usinglast known valid headings from the GPS. This method using absolute A/Gvalues for supplementing data to the GPS data when the GPS system haslost signal will find use in many applications outside of the automotiveindustry.

These elements in output signal format are made available to on boardGPS based navigation systems through a data port for supplementationduring periods of lost or down satellite signals so that the user of aGPS navigation system sees no down time during these periods.

In another aspect, since speed or velocity can be tracked by summingpositive and negative accelerations and multiplying by time, a secondmultiplication by time can yield distance, which is also useful innavigation.

Example 6 Altimeter Systems

In another aspect, summing positive and negative vertical accelerationsover time yields altitude. For example, an instrument, including anaccelerometer-gyroscopic sensor, placed in an airplane or other flyingobject, contains a circuit that continuously sums over all accelerationsand outputs altitude. Alternatively, a system including anaccelerometer-gyroscopic sensor included in a non-flying vehicle trackschanges in altitude and outputs a signal used to vary engine performanceor some other type of parameter.

This method of altitude determination has certain advantages overcurrent methods of determining altitude which rely on either radar,pressure sensors, or GPS triangulation. Of course its accuracy indetermining altitude above sea level (ASL) relies on knowledge ofinitial altitude, and its accuracy in determining altitude above groundlevel (AGL) relies on terrain maps or something similar. Since this typeof instrument would reveal nothing about a changing ground level belowan aircraft, any aircraft equipped with it would still require a radaraltimeter for determining AGL on instrument approaches that requiresuch.

Example 7 Dynamic Suspension Adjustment Systems

In some embodiments of this invention, outputs from the sensing oflateral acceleration are used to adjust suspension systems by stiffeningoutside suspension and/or loosening inside suspension of movingvehicles.

When lateral acceleration or force is applied to a vehicle, it tends tolean in the direction opposite to the force being applied, due in partto the softness of their suspension systems. This moves the center ofgravity further off center and in some cases outside of their wheelbaseapproaching the critical rollover point. Stiffening the outsidesuspension and/or loosening the inside suspension keeps the center ofgravity of vehicles within a tighter envelope relative to the wheelbase.This inversely affects the propensity, especially in high center ofgravity loaded vehicles, to rollover when the center of gravity of theirload exceeds the wheelbase and reaches the critical rollover point.Additionally, by adjusting the suspension system in this manner thedistribution of load between left and right side wheels is kept moreeven resulting in improved traction.

Typically these are configured as pulse width modulated (PWM)controlling devices. Such devices typically accept analog voltage levelinputs, which are then converted to a corresponding pulse width output.Such outputs are a common method of controlling and delivering aregulated amount of current to a device such as a hydraulic solenoid.The hydraulic solenoids of course are responsible for increasing,decreasing or maintaining pressure levels within the hydraulic orpneumatic suspension system.

An anti-rollover device 400 is illustrated in FIG. 4. In this embodimentvehicles are assumed to be equipped with adjustable suspension systems,typically hydraulic or pneumatic. When absolute lateral acceleration issensed the accelerometer-gyroscopic sensor 410 sends a signalrepresenting absolute lateral acceleration to a suspension selector 420,which passes signals along to a controller responsible for controllingthe relevant quadrant of the suspension. The suspension selector 420must interpret the signal to determine the appropriate quadrant. Forexample, Q1, in which suspension system 432 is controlled by suspensioncontrol 431 could be the right front wheel; Q2, in which suspensionsystem 442 is controlled by suspension control 441 could be the leftfront wheel; Q3, in which suspension system 452 is controlled bysuspension control 451 could be the right rear wheel; and Q4, in whichsuspension system 462 is controlled by suspension control 461 could bethe left rear wheel. Of course, other orderings are possible, as aresystems with only two independent zones, e.g. two sides are controlledin lockstep.

In other embodiments, simple lateral acceleration is provided to asuspension control system.

Of course, the present invention has additional uses that are notdiscussed in the embodiments above. The present invention has beendescribed in terms of specific embodiments incorporating details tofacilitate the understanding of the principles of construction andoperation of the invention. As such, references herein to specificembodiments and details thereof are not intended to limit the scope ofthe claims appended hereto. It will be apparent that those skilled inthe art that modifications can be made to the embodiments chosen forillustration without departing from the spirit and scope of theinvention.

1. A communication system for a vehicle, comprising: a. a vehicle speedsensor configured to emit a periodic function with a parametercorrelated to the speed of the vehicle; b. an acceleration monitoringsystem, configured to compute the acceleration of the vehicle fromvariations in the parameter of the periodic function and to output adeceleration status of the vehicle; c. a braking system engagementdetector to detect a braking status of the vehicle; d. an alertingdevice capable of signaling other drivers of a deceleration condition ofthe vehicle; and e. a control device coupled to the accelerationmonitoring system, the braking system engagement detector, and thealerting device, wherein the acceleration monitoring system sendssignals to the control device and the control device operates thealerting device in a manner dependent on the deceleration status of thevehicle.
 2. The communication system of claim 1, wherein the alertingdevice comprises lamps on the vehicle that are capable of flashing. 3.The communication system of claim 2, wherein the lamps are capable offlashing only at a constant rate.
 4. The communication system of claim2, wherein the lamps are capable of flashing at a variable rate, andfurther wherein the control device is configured to flash the lamps at arate correlated to a rate of deceleration.
 5. The communication systemof claim 2, wherein the lamps are one of the following: conventionalsignaling lamps and conventional brake lamps.
 6. The communicationsystem of claim 5, wherein the lamps are the lamps included on thevehicle during its original manufacture.
 7. The communication system ofclaim 5, wherein the control device further comprises a control systemfor the conventional brake lamp system, whereby the communication systemis an integrated control and circuitry system for all brake lamps. 8.The communication system of claim 5, wherein the existing control systemfor the conventional brake lamp system is substantially unmodified, andwherein the control device communicates with the conventional brake lampsystem in a substantially separate manner.
 9. The communication systemof claim 5, wherein the control device is in addition to a controlsystem for the conventional brake lamp system.
 10. The communicationsystem of claim 5, wherein one of the lamps is a center high mountedstop lamp.
 11. The communication system of claim 2, wherein the lampsare in addition to conventional brake lamps and conventional signalinglamps.
 12. The communication system of claim 2, wherein amber lights ofthe lamps are illuminated during deceleration.
 13. The communicationsystem of claim 2, wherein red lights of the lamps are illuminatedfollowing deceleration.
 14. The communication system of claim 12 or 13,wherein a light of the lamps is a bi-color light emitting diode.
 15. Thecommunication system of claim 1, wherein the control device receivessignals from the deceleration detector, the throttle engagementdetector, and the braking system engagement detector in cycles.
 16. Thecommunication system of claim 1, further comprising an input devicecoupled to the control device.
 17. The communication system of claim 16,wherein the input device comprises a throttle engagement detectorconfigured to relay a throttle status to the control device.
 18. Thecommunication system of claim 16, wherein the input device comprises aclutch engagement detector configured to relay a clutch status to thecontrol device.
 19. The communication system of claim 1, wherein oncethe braking system is engaged, a conventional brake lamp system isactivated and the communication system is de-activated.
 20. Thecommunication system of claim 19, wherein once the braking system isdisengaged, the communication system is re-activated.
 21. Thecommunication system of claim 1, wherein the alerting device comprises anon-visible radiation transmitter.
 22. The communication system of claim1, wherein the parameter is a frequency of the periodic function. 23.The communication system of claim 1, wherein the parameter is a pulsewidth of the periodic function.
 24. The communication system of claim 1,wherein the vehicle speed sensor includes a proximity sensor pairconfigured to detect rotation of a moving part of the vehicle.
 25. Amethod of alerting drivers in proximity to a vehicle of deceleration andbraking of the vehicle, comprising: a. sensing a speed of the vehicle;b. producing a periodic function with a parameter correlated to thespeed of the vehicle; c. determining a rate of acceleration of thevehicle based on variations in the parameter of the periodic function;d. detecting a braking status of the vehicle; e. detecting a throttlestatus of the vehicle; and f. if the vehicle is decelerating, emitting asignal to indicate that the vehicle is decelerating, wherein the signalvaries depending on the rate of deceleration, the braking status, andthe throttle status of the vehicle.
 26. The method of claim 25, whereinthe signal includes visible light.
 27. The method of claim 26, whereinsignal emitted flashes at a constant rate.
 28. The method of claim 26,wherein the flashes at a variable rate correlated to a rate ofdeceleration.
 29. The method of claim 26, wherein the signal is emittedthrough one of the following: conventional signaling lamps andconventional brake lamps.
 30. The method of claim 29, wherein the lampsare the lamps included on the vehicle during its original manufacture.31. The method of claim 29, wherein one of the lamps is a center highmounted stop lamp.
 32. The method of claim 26, wherein the signal isemitted through lamps that are in addition to conventional brake lampsand conventional signaling lamps.
 33. The method of claim 26, whereinthe signal is emitted by illuminating amber lights during deceleration.34. The method of claim 26, wherein the signal is emitted byilluminating red lights during stoppage.
 35. The method of claim 25,wherein the signal includes non-visible radiation.
 36. The method ofclaim 35, wherein the method further comprises: a. receiving the signalat a proximate vehicle in proximity to the decelerating vehicle; b.generating an alert signal to notify the driver of the proximate vehicleof the deceleration.
 37. The method of claim 35, wherein the non-visibleradiation is one of the following: infrared and radio frequency.
 38. Themethod of claim 25, wherein the parameter is a frequency of the periodicfunction.
 39. The method of claim 25, wherein the parameter is a pulsewidth of the periodic function.
 40. The method of claim 25, wherein thestep of sensing a speed of the vehicle comprises sensing a frequency ofrotation of a moving part of the vehicle.
 41. The method of claim 38,wherein the step of sensing a speed of the vehicle further comprisesconverting the frequency of rotation into a vehicle speed.